1. Field of the Invention
The present invention relates to a communication control technique in a wireless local network system configured by a plurality of independent wireless cells.
2. Description of the Related Art
For a wireless communication local network system including a plurality of independent wireless cells built using a plurality of access points connected to local networks, it is conventionally required to realize communication control according to QoS, and to provide satisfactory communication services.
To meet such requirements, it is effective to execute communication control according to the processing loads on respective access points, and various proposals about such communication control have been made so far.
For example, Japanese Patent Laid-Open No. 2004-80228 discloses a technique in which a wireless client terminal itself, which enjoys communication services, autonomously switches wireless cells associated by the wireless client terminal in accordance with a response speed from a server that provides the communication services.
Japanese Patent Laid-Open No. 2005-354423 discloses a technique in which a management apparatus that manages communication resources is provided on a network, and a wireless client terminal inquires the management apparatus upon setting a communication session, thereby preventing congestion in a wireless local network.
Furthermore, Japanese Patent Laid-Open No. 2004-221684 discloses a technique in which, when a control apparatus which systematically manages association information for respective wireless cells detects that the limited number of associates specified for each wireless cell has been exceeded, it selects a wireless client terminal of that wireless cell and instructs it to execute roaming.
However, in case of Japanese Patent Laid-Open No. 2004-80228, all wireless client terminals need to comprise a function of autonomously changing wireless cells to be associated in accordance with the response speed from the server. For this reason, when a wireless client terminal which does not implement this function is included, satisfactory communication services cannot be provided by the wireless local network system as a whole.
By contrast, when the management apparatus that manages the communication resources is independently arranged on the network like in Japanese Patent Laid-Open No. 2005-354423, the wireless client terminals need not implement the function. However, in case of Japanese Patent Laid-Open No. 2005-354423, the management apparatus merely determines whether or not to provide communication services by managing the communication resources, and no switching processing to another wireless cell is described.
On the other hand, in case of Japanese Patent Laid-Open No. 2004-221684, the control apparatus instructs a wireless client terminal to execute roaming so as to realize switching to another wireless cell. However, in case of the wireless communication local network system to be covered by the present specification, wireless cells built by respective access points are configured by “independent wireless cells”, and roaming cannot be applied intact to switching between independent wireless cells. Note that the independent wireless cells are wireless cells having different IEEE 802.11-based SSIDs (identifiers).